This project concentrates on prokaryote and eukaryote aminoacyl tRNA synthetases, enzymes which establish the rules of the genetic code by matching amino acids with trinucleotide sequences (contained within transfer RNA molecules). There are four components to the program: 1) Investigation of a covalent component to protein-nucleic acid (synthetase-transfer RNA) interactions; 2) Primary structures of and structure-function relationships between aminoacyl tRNA synthetases; 3) Synthesis of and structural relationships between mitochondrial and cytoplasmic forms of synthetases (in a eukaryote) which are specific for the same amino acid; 4) Regulation of aminoacyl tRNA synthetase biosynthesis.